The invention relates to a device for testing in a nondestructive manner in the course of the rolling process particularly hot, rod-shaped rolling stock above the Curie point, by means of a test coil system that rotates around the rolling stock passing through and which can be acted upon by a coolant, said test coil system consisting of at least two test coils.
Such devices are known per se, for example from GB-A-2 014 317. Said document shows (particularly in FIG. 2) a rotating test coil system that can be driven on rails to the test location, the latter being limited by the course of the rails. Said known device is conspicuous primarily on account of its long type of construction, which, in addition to the drawback that said it cannot be employed in any desired location, has the further disadvantages that exactly straight guidance of the material to be tested cannot be assured; that measurement errors may occur, on the one hand, and that the device may be damaged or even destroyed on the other.
Because of the length of the device, furthermore, feeding of the water for cooling and flushing both the coil and the rotating bearings is complicated and requires substantial expenditure.
Therefore, the invention is based on the problem of realizing a device of the type specified above in such a way that it can be installed in the form of a small structure in any desired location in the rolling mill where exact straight guidance of the rolling stock is naturally assured.
Said problem is solved by the invention according to the characterizing part of claim 1 in that the device is arranged directly downstream of the point where the rolled material exits from the rolling stand, specifically on the roll cooling system associated with said rolling stand; and in that the coolant for the test coil system is fed into the rotating system approximately in the plane in which the device is secured on the rolling stand. In said rotating system, provision is made for a coolant channel extending in the manner of a thread between the rolled material and the rotational bearing up to its face side, with individual ducts leading to the respective test coils in a radial manner.
Such an arrangement is particularly suitable in conjunction with so-called multi-roll rolling stands, where provision is made, for example for three rolls or rollers each being arranged offset by 120xc2x0 in relation to each other (a so-called Kocks block), and where in such a block a first roll triple is followed at a distance of about 35 cm by another roll triple. The device as defined by the invention is designed in such a way that it fits between the roll triples in said relatively confined space. Owing to the fact that the two roll triples follow each other so closely, exactly straight guidance of the rolling stock is assured, so that no further adjustment work is required after the device as defined by the invention has been set up and first adjustments have been made.
Furthermore, arranging the device as defined by the invention in the location (roll cooling system) specified in the characterizing part of claim 1 offers the further advantage that the cooling medium required for cooling the test coils is directly available in said location, and that said coolant, furthermore, can be directly fed there into the rotating part of the device within the zone where the device is secured. From there, the coolant can be passed through the channel extending in the manner of a thread, and guided to the individual test coils via the ducts branching off from said channel in a radial manner.
The thread-like channel is produced by cutting a thread-like groove into the surface of a cylinder belonging to the rotating part of the device. Said groove is covered by a second cylinder, which is pushed over the first cylinder.
The thread-like course of the coolant duct results in a large heat-absorbing surface that is located between the rolling stock and the rotating bearing and the signal transmitters, which are located in the rotating part of the device, on the one hand, and in the stationary part on the other. Said signal transmitters are connected to the test coils.
Especially in conjunction with the type of three-roll rolling stands described above, arranging the device as defined by the invention on the roll cooling system is suitable because the roll cooling system consists there of a channel surrounding the outlet for the rolled material in the form of a ring, whereby nozzle lines leading to the surfaces of the rolls are branching off from said channel in a radial manner. The stationary part of the device as defined by the invention is flanged to the housing surrounding the ring-shaped channel.
A particularly preferred embodiment of the test coils in the device as defined by the invention is specified in claim 3. In said embodiment, the test coils each are arranged on an approximately L-shaped support, specifically on the end of the longer leg of the xe2x80x9cLxe2x80x9d, and the support can be pivoted around an axle extending in the zone of the point of intersection of the legs. The supports, therefore, form angle levers.
Said design of the supports in the form of angle levers results in a point-symmetrical arrangement around the axis of the device. However, the important advantage offered by said design has to be seen in the swinging capability of the supports, by virtue of which it is possible to change the spacing of the individual test coils from the rolled stock to be tested.
The essential feature of the invention ensues in conjunction with the swinging capability of the supports of the test coils. Said feature is provided by claims 4 and 5 and specifies that the defined measuring position of the test coils is automatically assumed by said test coils only once defined parameters have been satisfied.
According to the features of claim 4, one of the legs of the L-shaped support is engaged by a spring that retains the test coil in a position that is removed from the rolled stock until a defined rotation frequency is exceeded, whereupon the test coil is driven into the measuring position as a result of increased centrifugal force.
Such a spring engages, for example the shorter leg of the xe2x80x9cLxe2x80x9d which has a counterweight making said leg heavier than the longer leg of the xe2x80x9cLxe2x80x9d. The spring ensures that the longer leg of the xe2x80x9cLxe2x80x9d with the test coil arranged thereon remains swung out of the measuring position until an adequate rotational speed of the test coil system has been reached. Said rotational speed is attained only if the leading end of the rolling stock to be measured (which naturally contains many impurities and errors and is later cut off, and which, furthermore, does not have the absolute straightness required for the measurement) has passed the measuring site. The frequency of rotation of the test coil system is adequately high for overcoming the force of the spring only then, and the shorter leg is then driven outwards due to the centrifugal force, which drives the test coil into the measuring position.
An alternative to the above is proposed by claim 5. According to claim 5, a pressure medium cylinder is arranged between the coolant feed to at least one test coil, and the short leg of the xe2x80x9cLxe2x80x9d of a test coil support disposed opposite said test coil. The piston of said cylinder is acted upon the shorter leg of the xe2x80x9cLxe2x80x9d via a bypass line by means of a piston rod as soon as the pressure of the coolant has exceeded a defined pressure value, causing the test coil to be pressed from a position removed from the rolling stock and into the measuring position. In the present case, too, the leading end of the rolling stock to be measured can be excluded during the measuring process by raising the pressure of the coolant to the required value only after said leading end has passed through, so that the small pressure medium cylinder is capable of pressing the test coil into the measuring position.
The lifted-off position can, be effected by spring force in the present case as well, but also by centrifugal force.
Although it is conceivable that each test coil or each test coil support can be equipped with a device according to claim 4 or claim 5, provision is preferably made according to the claim 6 that the swinging movements of the test coil supports are synchronized with each other. Such synchronization is accomplished with methods the expert in the field is familiar with (for example steering rod gear, rack-and-pinion gear, etc.).